Volume control device for electric musical instruments



Jan. 25, 1966 SHlGEAKl MABUCHI 3,231,659

VOLUME CONTROL DEVICE FOR ELECTRIC MUSICAL INSTRUMENTS Filed Sept. 26,1960 Source of szynal United States Patent 3,231,659 VOLUME CONTROLDEVICE FOR ELECTRIC MUSICAL INSTRUMENTS Shigeaki Mabuchi, Hamamatsu-shi,Japan, assignor to Nihon Gakki Seizo Kabushiki Kaisha, Hamamatsu-shi,Japan Filed Sept. 26, 1960, Ser. No. 58,235 Claims priority, applicationJapan, Apr. 6, 1960, 35/20,14'4 2 Claims. (Cl. 84-109) The presentinvention relates to a volume control device for electric musicalinstruments.

In prior electric musical instruments, volume control has been effectedby means of a variable resistor or an attenuator. However, since thevolume of an electric musical instrument is very frequently and quicklychanged, the former has short operating life and the latter isdisadvantageous in that it is inevitably accompanied by noise because itchanges the volume discontinuously. While in some cases variablecondensers have been used, they are not suitable for use in electricmusical instruments because of their narrow range of volume control.

It is the principal object of the present invention to provide, forelectric musical instruments, a long life circuit arrangement for volumecontrol having a Wide range of volume control without the accompanimentof the above-mentioned disadvantages.

Further objects and advantages of the present invention will becomeapparent, and this invention will be better understood from thefollowing description, taken in connection with the accompanyingdrawing, in which:

FIG. 1 is a connection diagram showing one embodiment of the presentinvention;

FIG. 2 shows a block diagram of the embodiment of FIG. 1.

Referring now to the accompanying drawing, more particularly to FIG. 2,an electric circuit utilizing a fixed resistor as an impedance Z, and afixed condenser as an impedance Z is known in the art as the Millersintegrating circuit. According to a feature of the present invention,variable condensers are used as said impedances Z and Z and also saidcondensers are connected to operate difierentially.

Referring to FIG. 1, let it be assumed that resistances R R and R aresufficiently larger than 1/wC and l/wC and R is approximately equal to Rand that the amplification factor of the vacuum tube is suflicientlylarge. Then, the following relation exists between the input voltage Eand the output voltage E Further, let it be assumed that in the casewhen the capacitance of the condenser C is changed from a value of C toa value of C capacitance of the condenser C differentially changes froma value of C to a value of C 3,231,659 Patented Jan. 25, 1966 ice andthat, in a particularly ideal case the values, C =C which means that thesound volume would change in proportion to the square of the change inthe capacitance.

Thus, for instance, when a differential condenser which can vary from 10pi. to pf. is used, the volume will be changed by 100 times (40 db),said range being sufficiently Wide for practical use.

The variable condenser utilized in the present circuit may be acondenser which is formed by slightly modifying a conventional variablecondenser, or it may be designed to have small angle of rotationespecially suitable for electric musical instruments.

In addition to the above, this invention is also characterized by thefact that the constant of the circuit can be varied in accordance withthe frequency sensitivity curve of the ear by suitably selecting theresistances R R and R Thus, it is possible to effect so-called loudnesscontrol. Since apparent impedances of various portions are considerablylow, it becomes possible to prevent noise from entering by suitablecare. It is desirable that the capacitances of the variable condensersutilized in the present circuit be linearly variable.

While the invention has been explained by describing a particularembodiment thereof, it will be apparent that improvements andmodifications may be made without departing from the scope of theinvention as defined in the appended claims.

What I claim is:

1. A volume controlled amplifier stagefor electronic musical instrumentswherein tones are generated by appropriate oscillator and filtercircuits, said amplifier stage comprising an electronic valve having acontrol electrode and a first and a second conductive electrode, aninput terminal for applying a generated tone to said control electrode,:an output terminal, means for connecting a load impedance across saidfirst and second conductive electrodes and to said output terminal, afirst resistor connected between said input terminal and said controlelectrode and adapted to apply saidinput signals to said controlelectrode, a second resist-or connected between said output terminal andsaid control electrode to feed output signals back to said controlelectrode, one end of each of said first and second resistors beingconnected together and to said control electrode, a third resistorconnected at one end to the junction of said first and second resistorsand said control electrode and at the other end to said secondconductive electrode and providing means in which the input signal andthe feedback signal combine algebraically, said feedback signal being inphase opposition to said input signal across said third resistor, afirst capacitor connected across said first resistor, a second capacitorconnected across said second resistor, and means for simultaneouslyvarying the capacitances of said first and second capacitors in oppositedirections to modify the relative impedances of the first and secondresistorcapacitor combinations to modify the amount of feedback signalapplied to said third resistor in relation to the amount of said inputsignal applied to said third resistor to determine "the amount ofcancellati-onof'said input signal and the References Cited by theExaminer UNITED STATES PATENTS 2,106,336 1/1 9318 .Andersonet-a'l. ,330155 X 2,113,332 4/1938 ,Morseet a1. 330-1 55 2,202,522 5/1940 Gloess..'3'30-97 X Hammond et a1. 841.26 X Firestone. Beanan et a1. 331-135Burwen 330107 X Meyer 841.25

OTHER REFERENCES Electronic Ana-log Computers, Kern and Korn, 1952,published by M-cGraW-Hill Book 00., Inc, New York 10 (pages 1211 and 150relied on).

GEORGE N. WESTBY, Primary Examiner. CARL W. ROBINSON, ARTHUR GAUSS,Examiners.

1. A VOLUME CONTROLLED AMPLIFIER STAGE FOR ELECTRONIC MUSICALINSTRUMENTS WHEREIN TONES ARE GENERATED BY APPROPRIATE OSCILLATOR ANDFILTER CIRCUITS, SAID AMPLIFIER STAGE COMPRISING AND ELECTRONIC VALVEHAVING A CONTROL ELECTRODE AND A FIRST AND A SECOND CONDUCTIVEELECTRODE, AN INPUT TERMINAL FOR APPLYING A GENERATED TONE TO SAIDCONTROL ELECTRODE, AN OUTPUT TERMINAL, MEANS FOR CONNECTING A LOADIMPEDANCE ACROSS SAID FIRST AND SECOND CONDUCTIVE ELECTRODES AND TO SAIDOUTPUT TERMINAL, A FIRST RESISTOR CONNECTED BETWEEN SAID INPUT TERMINALAND SAID CONTROL ELECTRODE AND ADAPTED TO APPLY SAID INPUT SIGNALS TOSAID CONTROL ELECTRODE, A SECOND RESISTOR CONNECTED BETWEEN SAID OUTPUTTERMINAL AND SAID CONTROL ELECTRODE TO FEED OUTPUT SIGNALS BACK TO SAIDCONTROL ELECTRODE, ONE END OF EACH OF SAID FIRST AND SECOND RESISTORSBEING CONNECTED TOGETHER AND TO SAID CONTROL ELECTRODE, A THIRD RESISTORCONNECTED AT ONE END TO THE JUNCTION OF SAID FIRST AND SECOND RESISTORSAND SAID CONTROL ELECTRODE AND AT THE OTHER END TO SAID SECONDCONDUCTIVE ELECTRODE AND PROVIDING MEANS IN WHICH THE INPUT SIGNAL ANDTHE FEEDBACK SIGNAL COMBINE ALGEBRAICALLY, SAID FEEDBACK SIGNAL BEING INPHASE OPPOSITION TO SAID INPUT SIGNAL ACROSS SAID THIRD RESISTOR, AFIRST CAPACITOR CONNECTED ACROSS SAID FIRST RESISTOR, A SECOND CAPACITORCONNECTED ACROSS SAID SECOND RESISTOR, AND MEANS FOR SIMULTANEOUSLYVARYING THE CAPACITANCES OF SAID FIRST AND SECOND CAPACITORS IN OPPOSITEDIRECTIONS TO MODIFY THE RELATIVE IMPEDANCES OF THE FIRST AND SECONDRESISTOR-CAPACITOR COMBINATIONS TO MODIFY THE AMOUNT OF FEEDBACK SIGNALAPPLIED TO SAID THIRD RESISTOR IN RELATION TO THE AMOUNT OF SAID INPUTSIGNAL APPLIED TO SAID THIRD RESISTOR TO DETERMINE THE AMOUNT OFCANCELLATION OF SAID INPUT SIGNAL AND THE AMPLITUDE OF SAID OUTPUTSIGNAL AT SAID OUPUT TERMINAL.